Enrichment of hepatic glycogen and plasma glucose from H₂18 O informs gluconeogenic and indirect pathway fluxes in naturally feeding mice

NMR Biomed. 2023 Feb;36(2):e4837. doi: 10.1002/nbm.4837. Epub 2022 Oct 22.


Deuterated water (2 H2 O) is a widely used tracer of carbohydrate biosynthesis in both preclinical and clinical settings, but the significant kinetic isotope effects (KIE) of 2 H can distort metabolic information and mediate toxicity. 18 O-water (H2 18 O) has no significant KIE and is incorporated into specific carbohydrate oxygens via well-defined mechanisms, but to date it has not been evaluated in any animal model. Mice were given H2 18 O during overnight feeding and 18 O-enrichments of liver glycogen, triglyceride glycerol (TG), and blood glucose were quantified by 13 C NMR and mass spectrometry (MS). Enrichment of oxygens 5 and 6 relative to body water informed indirect pathway contributions from the Krebs cycle and triose phosphate sources. Compared with mice fed normal chow (NC), mice whose NC was supplemented with a fructose/glucose mix (i.e., a high sugar [HS] diet) had significantly higher indirect pathway contributions from triose phosphate sources, consistent with fructose glycogenesis. Blood glucose and liver TG 18 O-enrichments were quantified by MS. Blood glucose 18 O-enrichment was significantly higher for HS versus NC mice and was consistent with gluconeogenic fructose metabolism. TG 18 O-enrichment was extensive for both NC and HS mice, indicating a high turnover of liver triglyceride, independent of diet. Thus H2 18 O informs hepatic carbohydrate biosynthesis in similar detail to 2 H2 O but without KIE-associated risks.

Keywords: fructose; gluconeogenesis; glycogenesis; isotope shift; triose phosphates.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blood Glucose* / metabolism
  • Fructose / metabolism
  • Gluconeogenesis
  • Glucose / metabolism
  • Glycerol
  • Liver / metabolism
  • Liver Glycogen* / metabolism
  • Mice
  • Phosphates / metabolism
  • Trioses / metabolism
  • Water / metabolism


  • Blood Glucose
  • Liver Glycogen
  • Glucose
  • Water
  • Glycerol
  • Trioses
  • Fructose
  • Phosphates